WO2018114110A1 - Fuel injector and method for operating a fuel injector - Google Patents

Abstract

The invention relates to a fuel injector (100), having an injection element (20) which is at least indirectly actuatable by a magnet armature (35; 35a; 35b), wherein the magnet armature (35; 35a; 35b) is arranged such that it can perform stroke movements along a longitudinal axis (21) within an injector housing (11) and, in the event of a magnet coil (45) that interacts with the magnet armature (35; 35a; 35b) being electrically energized with a current intensity (I₁, I₂), is movable counter to the spring force of a spring element (41) against a positionally fixed stroke stop (55), and wherein the stroke stop (55) is arranged in a radially outer region (56) of the magnet armature (35; 35a; 35b) in relation to the longitudinal axis (21).

Description

 description

Fuel injector and method of operating a fuel! Njektors prior art

The invention relates to a fuel injector according to the preamble of

Claim 1. Furthermore, the invention relates to a method for operating a fuel according to the invention! njektors.

A fuel injector according to the preamble of claim 1 is known from DE 2013 212 238 A1 of the applicant. The known fuel injector comprises a magnet armature, which is movable in the direction of the magnetic coil during the energization of a magnetic coil until the magnet armature bears axially against a stroke stop formed in the form of a residual air gap disk. The movement of the magnet armature serves to control the outflow of pressure medium (fuel) from a control chamber of the fuel injector in order thereby to control an opening or closing movement of a nozzle needle which releases or closes at least one injection opening formed in the injector housing.

The opening or closing characteristic of the magnet armature or the volume exiting from the control chamber during the lifting movement of the magnet armature per unit of time depends i.a. from the maximum armature stroke of the armature.

This armature stroke is dependent on a large number of components or their geometric dimensions and tolerances. It is essential that in still cold pressure medium or fuel, especially at relatively high

Press the system, after commissioning the fuel injector, the components of the fuel! heaters that affect the armature stroke, heat at different speeds. In particular, the magnet armature directly surrounded by the fuel is heated faster than the region of the injector housing, which is arranged in operative connection with the first stroke stop and thereby influences the maximum armature stroke. This results in commissioning of the fuel! njektors a reduced (maximum) armature stroke, which can be up to δμηη. From DE 10 2012 217 322 A1 of the Applicant, it is also known to form a magnet armature so elastic in a fuel injector, that during the interaction of the magnet armature with a stroke stop a

Optimization of the damping behavior by influencing the

 Quetschspaltes between the armature and the stroke stop can be achieved. The above-mentioned temperature-dependent problem of the armature stroke is not addressed in this document.

Disclosure of the invention

The fuel injector having the features of claim 1 has the advantage that during the entire operating period of the fuel injector, i. Especially during commissioning after starting an internal combustion engine, in which the maximum armature stroke influencing components of the

Fuel! Njektors different temperatures and thus have different dimensions due to different thermal expansions, a constant armature stroke is achieved.

The invention is based on the idea of making it possible, by means of a magnet armature designed or deformed elastically in the direction of movement of the magnet armature, for the magnet armature to achieve different (maximum) armature strokes due to different deformations as a function of the energization of a magnet coil. Due to the different armature strokes can thus compensate for the different temperatures of the armature stroke determining components of the fuel injector insofar as that in an otherwise occurring reduction of the (maximum) Ankerhubs a higher energization of the solenoid is selected, so that the armature to an additional armature stroke in the direction the stroke stop is deflected or moved.

Advantageous developments of the fuel injector according to the invention are listed in the subclaims. To form the elastically deformable magnet armature, it is provided in a structurally preferred embodiment that the armature at least on the magnetic core facing side is disc-shaped and has at least one weakening area. This weakening area causes the interaction with the stroke stop and

different levels of currents through the magnetic coil different areas of the armature deform different degrees and thus seen in total in the region of cooperating with the magnetic core

disc-shaped area to realize the different strokes.

In a preferred embodiment of the weakening region, this is formed by a slot arranged radially with respect to the longitudinal axis of the magnet armature. In particular, at least two, preferably three, slots arranged in mutually equal angular intervals relative to one another are provided as weakened areas. As a result, the magnet armature is divided in the region of its disc-shaped region into two or three circular segments.

Alternatively or additionally, however, it can also be provided that the weakened region is formed by a reduced in height or thickness portion of the magnet armature. Such a reduced section of the

Magnetic armature may be formed, for example, in the form of a groove or recess radially encircling the longitudinal axis in the magnet armature, so that the for the rigidity of the magnet armature in the disk-shaped area

substantial thickness through the groove or recess is reduced. Thereby, the region of the groove forms a kind of joint, which separates a radially inner region of the magnet armature from a radially outer region, wherein the radially outer region abuts the stroke stop, and the radially inner region is moved further in the direction of the magnetic core.

Furthermore, the variation of the maximum stroke of the magnet armature can additionally be influenced by the fact that the magnetic core facing the front side of the armature in a radially outer region and in register with the

Stroke stop (residual air gap disc) has a raised portion. This raised portion causes an increased distance to the magnetic core is formed in the radially inner region of the magnet armature, which is at least partially reduced at a stronger energization of the magnetic coil, thereby allowing an increased or increased armature stroke. In an alternative embodiment of the elastically deformable magnet armature, it is provided that the magnet armature at its

Outer circumference viewed in the circumferential direction has at least two sections with different sized diameters, wherein the portion with the larger diameter in coincidence with the stroke stop

 (Residual air gap disc) and the small diameter portion is disposed radially inside the stroke stopper. Thus, when energizing the magnetic coil, only the larger diameter portions of the armature must be deformed, which reduces the force required for deformation or increases the elasticity of the magnet armature.

In order to avoid magnetic adhesion of the magnet armature to the magnet core, the stroke stop is designed in particular in the form of a residual air gap disk. Such a residual air gap disc has the additional advantage that over the thickness of component tolerances of the rest, the armature stroke

determining components can be compensated.

The invention also includes a method for operating a fuel injector according to the invention so far described, wherein the magnet armature is pressed against a stroke stop during energization by a magnetic coil under elastic deformation. The inventive method is characterized in that the amount of current to the solenoid to

Influencing the elastic deformation of the armature and thus its armature stroke is selected time- or temperature-dependent. While a time-dependent energization of the magnet armature can be realized particularly easily and no means for determining the temperature of the pressure medium

(Fuel) needed in the fuel injector has a temperature-dependent

Energizing the armature has the advantage that the armature stroke can be set very precisely.

Regardless of the type of influencing the energization of the magnetic coil, it is also preferably provided that the amount of current flow, starting from a starting value, with increasing operating time of the

Fuel injector is reduced to a final value. It is provided that the starting value of the energization depending on the desired

(maximum) armature stroke is selected while the final value relates to the condition, in which the components of the fuel injector have assumed the same temperature.

Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments and from the drawing.

This shows in:

1 a fuel injector in the region of a switching valve in one

 Longitudinal section

Fig. 2

and

 Fig. 3 each in longitudinal section, the area of the switching valve at

 differently sized armature stroke,

Fig. 4

and

 Fig. 5 respectively in perspective view, differently designed

 Magnetic anchor and

Fig. 6

and

 Fig. 7 each in a partial longitudinal section, further embodiments of

 Magnetic anchor for the realization of different sized anchor strokes.

The same elements or elements with the same function are provided in the figures with the same reference numerals.

1, a fuel injector 100 is shown in fragmentary form, as it serves as a component for injecting fuel into a combustion chamber, not shown, of an internal combustion engine. The internal combustion engine is in particular a self-igniting internal combustion engine, wherein the

System pressure preferably, and not limiting, is more than 2000bar. The fuel injector 100 has a switching valve 10 which is arranged in the region of a recess 12 of the injector housing 11 in the region of a multipart injector housing 11. Within the recess 12, a valve member 15 is also arranged, which with an enlarged diameter, flange-like edge 16 axially on a shoulder 17 of the recess

12 is present. The valve piece 15 has a blind hole-shaped recess 19 in which a nozzle needle 20 serving as an injection member is guided in a lift-movable manner along a longitudinal axis 21. The injection needle 20 or the injection member is used in a conventional manner, the release or closing at least one, formed in the injector 1 1 injection port (not shown) for

 Injecting the fuel into the combustion chamber of the internal combustion engine. In the position of the nozzle needle 20 shown in FIG. 1, this is in its lower, i. the at least one injection opening occluding position shown. The nozzle needle 20 defines with the recess 19 in the valve piece 15 a

Control chamber 25 which can be filled via an inlet bore 26 from a high-pressure chamber 27 and pressure relief via a Abiaufbohrung 28 in a low-pressure region of the injector 1 1 and the fuel injector 100. About the pressure or the amount of pressure medium (fuel) located in the control chamber 25, the opening or closing movement of the nozzle needle 20 is controlled in a conventional manner. For this purpose, the drainage bore 28 can be closed or released via a sealing seat 31 formed on an outer surface of the valve piece 15 by means of a magnet armature 35 serving as a valve member 32. Serving as part of the switching valve 10 magnet armature 35 has in a sleeve-shaped portion 36 on the sealing seat 31 side facing a conical seat surface 37 which cooperates with lowered magnetic armature 35 with the sealing seat 31. In addition, the cross-section substantially hat-shaped armature 35 has a through hole 38, which serves for the radial mounting of the magnet armature 35 by means of an anchor bolt 39 to move the armature 35 in the direction of the longitudinal axis 21. The anchor bolt 39 is radially surrounded by a compression spring 41, which acts with its one end on the top of the armature 35 and axially supported with its other end face on a collar 42 of the anchor bolt 39, so that the armature 35 by means of the compression spring 41 in the direction of

Sealing seat 31 of the valve member 15 is subjected to force. In order to move the armature 35 against the spring force of the compression spring 41, this acts together with a likewise serving as part of the switching valve 10 magnetic coil 45, whose energization of a

Control device 50 can be influenced. The magnetic coil 45 is received in a radially around the longitudinal axis 21 circumferential recess 51 in a magnetic core 52. The magnetic core 52 is arranged on the side facing away from the valve piece 15 in operative connection with a closure lid 53, wherein further between the magnetic core 52 and the valve piece 15 a

Distance sleeve 54 is arranged. By means of the closure lid 53 is the

Valve member 15 via the magnetic core 52 and the spacer sleeve 54 axially clamped against the shoulder 17 in the recess 12.

In order to avoid an adhesion of the magnet armature 35 to the magnetic core 52 during energization of the magnetic coil 45, is also on the

 Magnet armature 35 facing side of the magnetic core 52 a preferably made of non-magnetic material residual air disc 55 arranged as a stationary stroke stop. In addition, the residual air gap disc 55 is used together with the spacer sleeve 54 for setting the maximum armature stroke of the magnet armature 35 during energization of the magnetic coil 45 and / or the

Tolerance compensation with respect to the maximum armature stroke determining components.

The magnet armature 35 is particularly formed in its magnetic core 52 and the magnetic coil 45 facing disc-shaped region 56, such that the region 56 has an increased deformability or elasticity in the direction of the longitudinal axis 21 to, as explained in more detail below, the maximum Armature stroke of the armature 35 to adjust or influence. For this purpose, reference is first made to the illustration of FIG. 1. The one shown there

Magnetic armature 35 has, in a section of the region 56 lying radially inside the residual air gap disk 55, a groove 60 which extends radially around the longitudinal axis 21 on the side facing the magnetic core 52

Weakening on, in the area of the thickness or height of the area 56 is significantly reduced by the groove 60. In contrast, the magnet armature 35a shown in FIG. 4 has by way of example, and not limitation, in its disk-shaped region 56 three first radial slots 58 arranged at equal angular intervals relative to each other, extending from the outer circumference of the region 56 and close to the through-hole 38 come up. In addition, the magnet armature points

35a purely by way of example, three further, also at regular angular intervals to each other arranged second radial slots 59, which also from

Extend the outer periphery of the area 56, but end at a greater radial distance from the through hole 38. Furthermore, the

Angular intervals between the first radial slots 58 and the second

Radial slots 59 of equal size, so that in each case between the radial slots 58, 59 acting in each case as weakening regions for the magnet armature 35a and the area 56 in the presence of a total of six radial slots 58, 59, a rotational angular distance of 60 ° between the radial slots 58, 59 results ,

On the outer circumference of the region 56, the magnet armature 35a moreover has three abutment portions 61 arranged at equal angular intervals around the throughbore 38 and projecting radially outwards, each having a relatively small extent in the circumferential direction, which interact with the residual air gap disk 55, so that the Diameter D of the magnet armature 35a is formed larger in the region of the abutment portions 61 than the diameter d in the areas in which no abutment portions 61 are provided. The diameters D, D are exemplified on the

Sizing or the diameter of the residual air gap disc 55 adapted that the abutment portions 61 are in register with the residual air gap disc 55, while the area 56 in the areas in which it has the smaller diameter d, radially within the residual air gap disc 55. By forming the radial slots 58, 59, the rigidity of the portion 56 of the magnet armature 35a is reduced. Here, the reduction of

Stiffness over the length and arrangement and number of radial slots 58, 59 and the thickness s of the area 56 can be influenced. In addition, the segments of the region 56, which have no abutment sections 61, do not participate in a deformation of the region 56 upon contact with the residual air gap disk 55 when the magnet coil 45 is energized. Fig. 5 shows an alternative in the perspective longitudinal section

designed armature 35b, in which the abutment portions 62 viewed in the circumferential direction of the region 56 each extend to the respective radial slots 58, 59 extend. In addition, it can be seen that the region 56 has a reduced thickness s in the region of the abutment sections 62.

The abutment portions 62 extend radially outward further than the wing-like portions (i.e., the portions without abutment portions 62) of the armature 35b in which the thickness s is not reduced. According to FIG. 6, it may optionally be provided to use the armature 35,

35a, 35b at its radially outer region with an example between 3μηι and 10μηι high level 64 equip that has a rectangular cross-section in the embodiment shown in FIG. In contrast, in the embodiment according to FIG. 7, the step 65 has a wedge-shaped shape in cross section, such that its height is in the radial direction

Direction increases.

2, a first operating state is shown, in which the magnetic coil 45 is energized by means of the control device 50 with a first current h. This current h causes the magnet armature 35 to move in the direction of

Magnet coil 45 against the spring force of the compression spring 41 until the

Magnet armature 35 with the magnetic core 52 facing end side of the residual air gap disc 55 axially abuts. It is essential that the first

Amperage h is selected such that, for example, no (elastic) deformation of the region 56 of the magnet armature 35 takes place. From the

 Energization of the solenoid coil 45 by means of the first current h thus results in a maximum armature stroke hi of the magnet armature 35 for controlling the outflow of pressure medium (fuel) from the control chamber 25. In FIG. 3, an operating state is shown in which the

Magnet coil 45 is energized by the controller 50 with a second current, the current b is greater than the current h. The increased current value b causes the portion 56 to be elastically deformed, so that the sleeve-shaped portion 36 whose seating surface 37 facing the seal seat 31 is substantially larger than the armature stroke magnitude i2 is pulled more toward the magnetic core 52 and the solenoid coil 45, respectively , This results a maximum armature stroke i2, which is greater than the armature stroke hi at a reduced energization of the magnetic coil 45th

The fuel described so far! Njektor 100 and the switching valve 10 with the armature 35, 35a, 35b can be modified or modified in many ways, without departing from the spirit. This consists in being able to set different armature strokes hi, i2 by a different high current supply to the magnet coil 45 in conjunction with a partially elastically deformable armature 35, 35a, 35b, in order to adjust the outflow of pressure medium from the control chamber 25 in an operationally dependent manner.

Claims

claims 1 . Fuel injector (100), with an at least indirectly by a magnet armature (35;  35a; 35b) actuatable injection member (20), wherein the magnet armature (35; 35a; 35b) along a longitudinal axis (21) liftable within an injector (1 1) is arranged and when energizing a with the magnet armature (35; 35a; 35b) cooperating magnetic coil (45) having a current (h,) against the spring force of a spring element (41) against a stationary  Stroke stop (55) is movable, and wherein the stroke stop (55) with respect to the longitudinal axis (21) in a radially outer region (56) of the armature (35; 35a; 35b) is arranged, characterized in that the magnet armature (35; 35a, 35b) in the direction of the longitudinal axis (21)  considered elastically deformable, and that of the  Magnetic coil (45) acting on the armature (35; 35a; 35b)  Attraction for achieving different maximum maximum lift strokes (hi, i2) by different maximum current levels (,)  is changeable. 2. Fuel injector according to claim 1,  characterized,  in that the magnet armature (35; 35a; 35b) at least on the magnetic core  (52) facing side in its radially outer region (56)  is disc-shaped, and that the magnet armature (35; 35a; 35b) has at least one weakening region. 3. Fuel! A nudger according to claim 2,  characterized, the weakened region is formed by a slot (58, 59) arranged radially in relation to the longitudinal axis (21). Fuel injector according to claim 2 or 3,  characterized,  the weakened region is formed by a section of the magnet armature (35; 35a; 35b) which is reduced in height (s) and / or by a groove (60) running around the longitudinal axis (21) at least in regions. 5. Fuel injector according to one of claims 2 to 4,  characterized,  in that the end face of the magnet armature (35; 35a; 35b) facing the magnetic core (52) has a raised portion (64,65) in the radially outer region (56) and coinciding with the stroke stop (55). 6. Fuel injector according to one of claims 2 to 5,  characterized,  in that the magnet armature (35a, 35b) is provided on its outer circumference in  The armature (35a, 35b) has an enlarged diameter (D), wherein the abutment portion (61, 62) is arranged in radial overlap with the stroke stop (55), and in that the regions of the magnet armature (35a; 35b) extend radially outside of the abutment portion (61; 62) within the stroke stop (55). Fuel injector according to one of claims 1 to 6,  characterized,  the stroke stop (55) is designed in the form of a residual air gap disk. Fuel injector according to one of claims 1 to 7,  characterized, in that the magnet armature (35; 35a; 35b) is formed on the side facing away from the magnet coil (45) at least indirectly for controlling the outflow of a pressure medium from a control chamber (25). Method of operating a fuel! A njektors (100), which is formed according to one of claims 1 to 8, wherein the magnet armature (35; 35a; 35b) is pressed during energization by a magnetic coil (45) under elastic deformation against the stroke stop (55), characterized, the height of the maximum current (h,) of the magnetic coil (45) for influencing the elastic deformation of the magnet armature (35; 35a; 35b) and thus of the maximum armature strokes (hi, i2) is selected as a function of operation. Method according to claim 9, characterized, that the height of the maximum amperage (h,), starting from a Start value, with increasing operating time of the fuel injector (100) is reduced to a final value.